This invention relates to passive alignment of optical elements, particularly optical fibers, with other optical elements.
Optical waveguide devices formed on substrates are often referred to as planar integrated optical devices or planar photonic devices. When an optical waveguide device is to be utilized in an optical communication system, it is usually coupled to at least one optical fiber or an optical element at one point, and often at many points, on the substrate. An optical waveguide device which has been coupled to lengths of optical fibers for ease of insertion into an optical system is sometimes referred to as a xe2x80x9cpigtailedxe2x80x9d waveguide device by those skilled in the art. Light propagates through the core region of optical fibers, and these core regions can be as small as a few microns in diameter. Alignment of the fiber to the waveguide on the substrate is critical to ensure efficient light coupling between the fiber and the waveguide. Various articles exist to align optical fibers to substrates incorporating optical waveguide devices. The need for critical alignment tolerances has resulted in a high degree of complexity and cost for these devices and methods of the prior art. There are many descriptions of methods which utilize silicon V-grooves as a positioning element, which are based on the preferential etching of certain crystalline orientations of silicon. This is accomplished by a series of lithographic steps including resist coating and exposure, followed by liquid etching. However, the V-groove, once fabricated, serves only to position the optical fiber relative to the surface of the silicon wafer. It still remains to position the fiber end relative to the waveguide end. This is usually accomplished by micromanipulation of the two components relative to each other followed by fixing of the alignment with an optical quality glue or adhesive. Micromanipulation is an expensive and time-consuming process when used in the manufacturing operation. Alternatively, the V-groove and optical fiber can be positioned relative to the waveguide by the use of additional positioning elements, but these also increase the complexity and cost of the method. Also, the V-groove techniques serve to position an optical fiber relative to some surface, such as that of the silicon itself, but the V-groove does not provide any force to retain the optical fiber in position. That is, the optical fiber can easily slip out of the groove unless one or more additional elements are present to provide some retaining force. Typically, a cover plate or a second substrate containing V-grooves is forced down in contact with the optical fibers to hold them in the V-grooves and optical cement or photopolymer is used to hold the assembly together.
Several methods and devices exist for positioning optical fibers on a substrate which also includes a waveguide or integrated optical device. However, the techniques are complex or they lack the sufficient retaining force necessary to provide a simple, low-cost, yet effective method of providing such a coupling. Thus, a need exists for devices and methods which allow for simple, accurate positioning of optical fibers to optical waveguides on a variety of desirable substrates. It would also be desirable to provide methods and devices that do not require many additional manufacturing steps or positioning elements or elaborate alignment by micromanipulators and which provide a secure retaining force to the optical fiber without the need for additional elements held in place by optical adhesives or thermal heat treatments.
Certain embodiments of the invention relate to methods and articles for manufacturing pigtailed planar optical devices. The various embodiments of the present invention provide relatively simple and inexpensive methods and articles for aligning optical elements such as optical fibers with another optical element on a substrate. The methods and articles do not require adhesives for securing the fibers to substrates. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.